1. Technical Field of the Invention
The present invention relates to a flash emitting device that is used, as a heat source, for heat-treating a workpiece such as one or more semiconductor wafers, semiconductor boards and liquid crystal boards, and to a radiant heating apparatus having a flash emitting device.
2. Description of Related Art
In recent years, since it is required that a surface layer portion of a workpiece such as a semiconductor wafer be heated at a desired temperature for a very shot time, it has been examined whether a flash discharge apparatus having a flash discharge lamp can be used as a heat source.
On the other hand, semiconductor wafers having a 100 to 200 mm diameter are popular. Further, semiconductor wafers having a larger diameter such as a 300 mm diameter wafer have been used. It is difficult to uniformly heat such a large semiconductor wafer at a high temperature for a very short time by the flash discharge lamp.
Accordingly, to put such a radiant heating apparatus having a flash discharge lamp into practice, as a heat source, flash emitting devices having a plurality of flash discharge lamps that are in parallel arranged at even intervals and a common reflector of all the flash discharge lamps, have been developed.
However, in such a radiant heating apparatus having the flash emitting device, flash lights emitted from the flash discharge lamps are overlaid on a workpiece such as a semiconductor wafer. Actually, the intensity of the overlaid flash lights emitted on a side portion of the semiconductor wafer is lower than that of the light emitted on the center portion of the semiconductor wafer. As a result, since the intensity of the flash light is not enough to heat the entire surface of the workpiece, the entire surface of the workpiece is not uniformly heated.
It is an object of the present invention to uniformly heat a workpiece such as one or more semiconductor wafers.
It is another object of the present invention to provide a flash emitting device which is capable of uniformly heating a workpiece such as one or more semiconductor wafers with the relatively small number of flash discharge lamps.
It is a further object of the present invention to provide a radiant heating apparatus having a flash emitting device which is capable of uniformly heating a workpiece such as one or more semiconductor wafers with a relatively small number of flash discharge lamps.
The present invention provides a flash emitting device having a plurality of flash discharge lamps arranged in parallel, in which a flash from the plurality of flash discharge lamps is emitted on a workpiece. The flash emitting device comprises main condensers each of which connected to one of the plurality of flash discharge lamps, wherein among the plurality of flash discharge lamps, at least one flash discharge lamp located on at least one side of the flash emitting device emit light with higher intensity than that of the plurality of flash discharge lamps other than said at least one flash discharge lamp.
The present invention further provides a flash emitting device in which a flash from the plurality of flash discharge lamps is emitted on a work piece. The flash emitting device comprises a plurality of flash discharge lamps arranged in parallel wherein at least one of the plurality of flash discharge lamps is a side flash discharge lamp located on at least one side of the flash emitting device and at least one of the plurality of flash discharge lamps is a center flash discharge lamp located on at least a center of the flash emitting device, at least one side main condenser, each of which is connected to one of the at least one side flash discharge lamps; at least one center main condenser, each of which is connected to one of the at least one center flash discharge lamps; wherein a voltage to which the at least one side main condenser is charged is higher than the voltage to which said at least one center main condenser are is charged.
The flash emitting device may include a first direct current power source for supplying power to the at least one center main condenser and a second direct current power source for supplying power to the at least one center main condenser.
The flash emitting device may further include a charge time controller in which the voltage to which the at least one center main condenser is charged is controlled so as to be lower than that to which the at least one side main condenser is charged, by charging the at least one center main condenser for a shorter time than that for the at least one side main condenser.
The flash emitting device may furthermore include a discharge controller in which the voltage to which the at least one center main condenser is charged is controlled to be lower than the voltage which the at least one side main condenser is charged, by discharging charges accumulated in the at least one center main condenser.
The flash emitting device may further include a chamber in which the workpiece is placed and flash lights from the plurality of the at least one side flash discharge lamp and the at least one center flash discharge lamp are emitted onto the workpiece.
The workpiece may be one or more semiconductor wafers.
The present invention furthermore provides a radiant heating apparatus comprising a flash emitting device having a plurality of flash discharge lamps arranged in parallel, in which a flash from the plurality of flash discharge lamps is emitted onto a workpiece, the flash emitting device comprising; a plurality of main condensers corresponding to the plurality of flash discharge lamps, wherein at least one of the plurality of flash discharge lamps, is located on at least one side of the flash emitting device and emits light with a higher intensity than light emitted from the plurality of flash discharge lamps located on another side of the flash emitting device.
According to the present invention, in the flash emitting device, the capacity of all the main condensers corresponding to the plurality of flash discharge lamps respectively is substantially the same.
Further, the voltage to which each of the side main condensers is charged is higher than any one of the center main condensers. Therefore, the full-width half maximum (FWHM) of the waveform of flash light emitted from each of the side flash discharge lamps agrees with the full-width half maximum (FWHM) of the waveform of flash light emitted from each of the center flash discharge lamps. Furthermore, a peak reaching time of the waveform of the flash light emitted from each of the side flash discharge flash lamps does not differ from that of the waveform of the flash light emitted from each of the center flash discharge lamps. (xe2x80x9cpeak reaching timexe2x80x9d means a time period for light emitting energy to reach the peak energy level.)
Since the emitting light energy of the flash light emitted from each of the side flash discharge lamps is higher than that of the flash light emitted from each of the center flash discharge lamps, it is possible to make the intensity of light emitted on the side area of the workpiece substantially the same as that of light emitted on the center area of the workpiece.